Just import the .h file wherever you want to use your new methods, and call them like you would any other NSMutableArray methods.

Good luck and Keep on Coding!

Solution:2

I wouldn't say that using NSMutableArray is necessarily the best solution, particularly if you're adding methods with categories, due to the fragility they can cause if method names collide. For a quick-n-dirty queue, I'd use the methods to add and remove at the end of a mutable array. However, if you plan to reuse the queue, or if you want your code to be more readable and self-evident, a dedicated queue class is probably what you want.

Cocoa doesn't have one built in, but there are other options, and you don't have to write one from scratch either. For a true queue that only adds and removes from the ends, a circular buffer array is an extremely fast implementation. Check out CHDataStructures.framework, a library/framework in Objective-C that I've been working on. It has a variety of implementations of queues, as well as stacks, deques, sorted sets, etc. For your purposes, CHCircularBufferQueue is significantly faster (i.e. provable with benchmarks) and more readable (admittedly subjective) than using an NSMutableArray.

One big advantage of using a native Objective-C class instead of a C++ STL class is that it integrates seamlessly with Cocoa code, and works much better with encode/decode (serialization). It also works perfectly with garbage collection and fast enumeration (both present in 10.5+, but only the latter on iPhone) and you don't have to worry about what is an Objective-C object and what is a C++ object.

Lastly, although NSMutableArray is better than a standard C array when adding and removing from either end, it's also not the fastest solution for a queue. For most applications it is satisfactory, but if you need speed, a circular buffer (or in some cases a linked list optimized to keep cache lines hot) can easily trounce an NSMutableArray.

Solution:3

As far as I know, Objective-C does not provide a Queue data structure. Your best bet is to create an NSMutableArray, and then use [array lastObject], [array removeLastObject] to fetch the item, and [array insertObject:o atIndex:0]...

If you're doing this a lot, you might want to create an Objective-C category to extend the functionality of the NSMutableArray class. Categories allow you to dynamically add functions to existing classes (even the ones you don't have the source for) - you could make a queue one like this:

(NOTE: This code is actually for a stack, not a queue. See comments below)

Solution:4

There's no real queue collections class, but NSMutableArray can be used for effectively the same thing. You can define a category to add pop/push methods as a convenience if you want.

Solution:5

Yes, use NSMutableArray. NSMutableArray is actually implemented as 2-3 tree; you typically need not concern yourself with the performance characteristics of adding or removing objects from NSMutableArray at arbitrary indices.

Solution:8

The solutions that use a category on NSMutableArray are not true queues, because NSMutableArray exposes operations that are a superset of queues. For example, you should not be allowed to remove an item from the middle of a queue (as those category solutions still let you do). It is best to encapsulate functionality, a major principle of object oriented design.

Solution:9

Use NSMutableArray.

Solution:10

Is there some particular reason you cannot just use the STL queue? Objective C++ is a superset of C++ (just use .mm as the extension instead of .m to use Objective C++ instead of Objective C). Then you can use the STL or any other C++ code.

One issue of using the STL queue/vector/list etc with Objective C objects is that they do not typically support retain/release/autorelease memory management. This is easily worked around with a C++ Smart Pointer container class which retains its Objective C object when constructed and releases it when destroyed. Depending on what you are putting in the STL queue this is often not necessary.

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